Materials

ABSTRACT

A composite surface material comprising a permeable substrate and a permeable surface layer bonded to the substrate so that the material is permeable.

This invention relates to materials, particularly, but not exclusively,materials for surfacing paths, driveways, roadways and outdoor hardstanding areas, methods of making them and methods of using them.

Porous sheet containing crumb rubber is known from GB767957, and is saidto be useful as a carpet underlay or carpet backing. Sports and domesticsurfaces made from materials including crumb rubber are known fromUS2006/0124031, the crumb rubber being incorporated in an asphaltmatrix, and from US2008/0104814 and US 2004/0069924 in which an expandedpolypropylene (EPP) product. is spread in situ or factory-formed intotiles or blocks and laid on a prepared base such as concrete or as asuspended floor, and covered with a surface finishing material of crumbrubber, hardwood flooring or carpet.

Crumb rubber is recovered from automobile and ground-running tyres,which contain wire. For use in surfacing materials, the rubber has to becompletely separated from the wire, which would constitute a hazard,projecting randomly from the surface.

The present invention provides new surface materials, new ways of makingthem and new uses for them exhibiting substantial advantages overprevious products.

The invention comprises a composite surface material comprising apermeable substrate and a permeable surface layer on the substrate sothat the material is permeable.

The substrate may comprise particulate material bound in a permeableresin matrix

The particulate material may comprise a recycled material such as rubbercrumb, which may be recovered from automobile and other ground wheeltyres. For most purposes for which shredded tyres are used, it isnecessary for the crumb to be free from wire, sharp ends of which couldbe a hazard. However, for the present purpose, as the crumb is used in asubstrate, it is not necessary to separate out all the wire, whichresults in a cost saving.

Other particulate materials can be used instead of or in addition to therubber crumb, for example recycled nitrile rubber contaminated with polyvinyl chloride (pvc) recovered from scrapped window frames. Theparticulate material need not, of course, be or contain recycledmaterial, but generally speaking recycled material is less expensivethan new material.

The permeable resin matrix may set hard, so that the product is rigid.

The matrix may contain connected voids through which water can flow.

The permeable surface layer may comprise conventional paving or flooringmaterial such for example as stone aggregate or chippings, rubber crumb,metal mesh and mosaic tiles as may be desired for the sake ofappearance, wear, traction and other properties. Such material may beloose, or may also be bound in a resin matrix, which may comprise asimilar resin system to that of the substrate, or a different system,but compatible therewith so that it can be bonded thereto.

Different resins may be used in the substrate and the surface layer,which may be set at different temperatures and which may be thermallybonded together at an elevated temperature. The resin in the substrateneed have no special properties except to set and bond to theparticulate inclusion, and can therefore be inexpensive. It may bedesired, however, to use a resin in the surface layer that does notdiscolour in sunlight. The resin in any case may be a two-part resin.

The rubber crumb may have a particle size up to 100 mm, and theparticles may be uniform in size or may have a range of sizes, e.g.between 50 mm and 100 mm, or 20 mm and 50 mm. Permeability may beentirely due to gaps between particles not being filled with the resinmatrix. Generally, larger particles will result in larger gaps andgreater permeability.

The ratio of resin to particulate material in the substrate may bebetween 6 and 15% by weight, and may in particular be 10%. In thesurface layer, if stone aggregate is used, the ratio of resin to stonemay be about 6% by weight,

The composite material may have a permeability such that surface waterreadily soaks through it, and may have a permeability of the order of10,000 litres per square metre per hour, for instance, at least 1,000litres per square metre per hour. Such a permeability allows rainwaterto soak away—depending, of course, on the underlying groundcondition—and the material is useful as a paving for hard standing ingarden areas, for example, which might be paved over as a lowmaintenance area or for vehicular parking. Conventional impermeablepaving, such as asphalt and slabs laid on concrete, over such areas hasbeen cited as a cause of flooding by directing excessive volumes ofrainwater into street drains that were not designed or are notmaintained to cope with such volumes.

The composite material may be spread in situ in two steps, with theresin matrix of the substrate being allowed to cure, or at leastpartially cure, before spreading the surface layer.

The material may be spread as a dispersion of particles in a liquidresin, or the particles may be spread dry and resin poured or sprayed onto the particles.

Or the substrate may be spread, in either of the above fashions, and thesurface layer separately formed as tiles or slabs, which are laid on topafter the substrate resin system has cured or partially cured.

Or the composite material may be formed as two (or more) layer tiles orslabs.

In one method for making tiles or slabs, the rubber crumb substrate isfirst cast in a mould, then the surface layer cast on top of thesubstrate.

The mould may be a two part mould having a lower part having a firstdepth for the substrate, allowing the substrate to be trowelled orlayered in to that first depth, and an upper part, that can be locatedon the lower part, having a second depth, into which the surface latercan be cast. The mould may for instance be 450×450 mm square, the lowerpart having a depth of, say, 20 mm, the upper part having a dept of,say, 10 mm.

The mould may be fabricated out of a high molecular weight, high-densitypolyethylene or other material to which the resin systems do not adhere,or at lease have a release lining of such material. The tiles or slabsmay be removed from the mould when cured or partially cured and stackedto cure completely before shipping or deployment.

The slabs or tiles may be made in a continuous process in which mouldsare moved along a rack which may pass through ovens in whichpredetermined temperatures may be maintained.

The invention also comprises a water management system in which a pit isfilled with a permeable substrate with a permeable surface layerthereon. The substrate may contain rubber crumb, and the surface layermay comprise stone aggregate, rubber crumb or any other particulatematerial with appropriate wear, appearance, traction and otherproperties, which may also be bound in a resin matrix. Such a pit may befilled with a homogeneous depth of material, with uniform particle size,or with a uniform range of particle sizes, or may be filled with agraded particle size distribution, for example, larger particles at thebottom, smaller at the top.

Such a pit may act as a soakaway to accommodate excess water from flashfloods and feed it to drains, and may be provided with a pump, which maybe automatically activated by, for example, a level sensor or moisturesensor, and may be powered from a battery charged by e.g. solar or windenergy.

Embodiments of composite surface material, methods for making the same,and a water management system according to the invention will now bedescribed with reference to the accompanying drawings, in which:

FIG. 1 is a section through one embodiment of surface material;

FIG. 2 is a perspective view of a slab or tile of the surface materialof FIG. 1;

FIG. 3 is a side elevation of a mould for making the slab or tile ofFIG. 2;

FIG. 4 is a perspective view of in situ laying a surface material;

FIG. 5 is a cross section through a soakaway comprising anotherembodiment of surface material; and

FIG. 6 is a view through a lens of the material of FIG. 1 in crosssection.

The drawings illustrate a composite surface material 11 comprising apermeable substrate 12 and a permeable surface layer 13 bonded to thesubstrate 12 so that the material 11 is permeable.

The substrate 12 comprises particulate material 14 (FIG. 6) bound in aresin matrix 15.

The particulate material comprises rubber crumb 14, which can berecovered from tyres, from which wire has not necessarily beencompletely separated. As the crumb 14 is in a substrate, projecting endsof wire will not appear on the surface.

The resin matrix 15 is chosen so as to set hard, unlike carpet underlay,so that the product is rigid. The matrix 15 is not homogeneous, butcontains connected voids, through which water may flow. Thisparticularly results from the proportions of resin and particulatematerial in the mix, which is around 10% resin to 90% particulatematerial

The rubber crumb has a particle size up to 100 mm, and the particles maybe uniform in size or may have a range of sizes, e.g. between 50 mm and100 mm, or 20 mm and 50 mm. Permeability is entirely due tointerconnecting voids between particles. Generally, larger particleswill result in larger interconnected voids and so greater permeability

The permeable surface layer 11 comprises conventional paving or flooringmaterial, in this instance, stone aggregate or chippings 18, althoughrubber crumb, metal mesh and mosaic tiles as may be desired for the sakeof appearance, wear, traction and other properties. Such material isalso bound in a resin matrix 15, which is chosen so as to be resistantto ultraviolet discolouration, but compatible with the resin of thesubstrate so that it can be bonded thereto. When different resins areused in the substrate and the surface layer, they may be set atdifferent temperatures and may be thermally bonded together at anelevated temperature. In the substrate, a methylene diphenyldiisocyanate resin can be used, while a UV stabilised aliphaticpolycyanate resin can be used in the surface layer 11. The ratio ofresin to stone aggregate is about 6% resin to 94% stone—stone is denserthan crumb, and the volume ratio is roughly the same. If a less denseparticulate material is used, such as rubber crumb, theresin/particulate ratio will be higher, about 1:10 as for the substrate.

FIG. 2 illustrates a tile or slab 21 having the substrate and surfacelayers 12, 13, the latter incorporating stone aggregate 18. The tile orslab 21 can be of any desired dimensions, for example 450 mm×450 mm,with the substrate being 20 mm deep and the surface layer being 10 mm—inFIG. 2 the depth scale is exaggerated.

FIG. 3 illustrates a two-part mould 31 having a lower part 32 forforming the substrate 12 and a separate upper part 33 that registerswith the lower part 32 by means of dowels 34 engaging in bores 35. Withthe upper part 32 removed, substrate material is loaded into the lowerpart 32, either as a dispersion of the rubber crumb in liquid resin, orby loading the crumb dry and pouring or spraying resin on top, andlevelling off. When cured or partially cured, the upper part 33 isadded, and the surface later cast on top of the substrate. After curingor partial curing the resins may be activated to bond at an elevatedtemperature. The cured or partially cures slab or tile can be removed tobe stacked for storage or transportation. The resins may complete theircuring while so stacked.

The mould 31 can be made of plastics material from which the cured orpartially cured slab or tile can be easily released, or made from e.g.metal components covered in such plastic. Likewise, a pallet on whichthe tiles are stacked might be covered in a release liner, which mayalso be interleaved with the tiles or slabs.

FIG. 4 illustrates a method for laying a permeable surface layer insitu. In which the ground is excavated to the required depth and thesubstrate 12 is laid, either as a dispersion of rubber crumb in a liquidresin or as dry rubber crumb on to which liquid resin is sprayed orpoured, and left to cure or partially cure after being levelled off byraking or rolling. The surface layer 13 is then applied in similarfashion, or it may be applied in the form of tiles as illustrated inFIG. 2, or even just as an upper layer formed into a tile without itssubstrate.

FIG. 5 illustrates a water management system comprising a pit 51containing a resin/rubber crumb substrate 52 and a surface layer 53—thisis essentially a tile like that illustrated in FIG. 2, but withsubstantially greater depth.

The substrate 52 is made in three parts, 52 a, 52 b and 52 c in whichuppermost layer 52 a had crumb particle sizes of 50-100 mm. Layer 52 bhas particle sizes of 28-20 mm, and the lowermost layer 52 c hasparticle sizes of 10-25 mm. The surface layer 53 includes stoneaggregate as in FIG. 2.

This constitutes a soakaway capable of absorbing surface water veryquickly. For severe or prolonged flooding, a pump 54 is activated by alevel sensor 55 to pump water from the pit 51, whence it can be directedto street drains or otherwise. The pump is powered from a battery 56charged by a solar panel 57.

Composite surface materials as described above can be used in numeroussituations where management of water is required, for example in pathssand driveways, where thee material may bee laid on top of a geotextilebarrier, for example for weed control, or in sea walls and sea defences,where the permeable nature of the material may dissipate wave forces,and for protection against erosion of beaches and dunes, and of riverand canal banks.

1. A composite surface material comprising a permeable substrate and apermeable surface layer on the substrate so that the material ispermeable.
 2. A material according to claim 1, in which the substratecomprises particulate material bound in a permeable resin matrix
 3. Amaterial according to claim 2, in which the particulate materialcomprises a recycled material.
 4. A material according to claim 3, inwhich the recycled material comprises rubber crumb, which may berecovered from automobile and other ground wheel tyres.
 5. A materialaccording to claim 4, in which the crumb has been shredded without firstremoving all the wire.
 6. A material according to claim 2, containingparticulate material other than rubber crumb.
 7. A material according toclaim 6, comprising recycled nitrile rubber contaminated with poly vinylchloride (pvc) recovered from scrapped window frames.
 8. A materialaccording to claim 2, in which the permeable resin matrix sets hard, sothat the product is rigid.
 9. A material according to claim 2, in whichthe matrix contains connected voids through which water can flow.
 10. Amaterial according to claim 2, in which different resins are used in thesubstrate and the surface layer.
 11. A material according to claim 10,in which the resins are set at different temperatures.
 12. A materialaccording to claim 10, in which the resins are thermally bonded togetherat an elevated temperature.
 13. A material according to claim 10, inwhich the resin in the surface layer does not discolour in sunlight. 14.A material according to claim 2, in which a two part resin is used. 15.A material according to claim 1, in which the particulate material inthe substrate has a particle size up to 100 mm.
 16. A material accordingto claim 15, in which the particles are uniform in size.
 17. A materialaccording to claim 15, in which the particles have a range of sizes. 18.A material according to claim 17, in which the particles are sizedbetween 50 mm and 100 mm.
 19. A material according to claim 17, in whichthe particles are sized between 20 mm and 50 mm.
 20. A materialaccording to claim 2, in which permeability is entirely due tointerconnected gaps between particles not being filled with the resinmatrix.
 21. A material according to claim 2, in which the ratio of resinto particulate material in the substrate is between 6 and 15% by weight.22. A material according to claim 2, in which the ratio is 10%.
 23. Amaterial according to claim 2, in which, in the surface layer, stoneaggregate is used, and the ratio of resin to stone is about 6% byweight.
 24. (canceled)
 25. A material according to claim 1, having apermeability such that surface water readily soaks through it.
 26. Amaterial according to claim 25, having a permeability of the order of10,000 litres per square metre per hour, and at least 1,000 litres persquare metre per hour.
 27. A material according to claim 26, used as apaving for hard standing in garden areas.
 28. (canceled)
 29. (canceled)30. (canceled)
 31. (canceled)
 32. (canceled)
 33. (canceled) 34.(canceled)
 35. (canceled)
 36. (canceled)
 37. (canceled)
 38. (canceled)39. (canceled)
 40. A water management system in which a pit is filledwith a composite surface material according to claim
 1. 41. (canceled)42. A system according to claim 40, filled with a homogeneous depth ofmaterial, with uniform particle size, or with a uniform range ofparticle sizes,
 43. A system according to claim 40, filled with a gradedparticle size distribution, for example, larger particles at the top,smaller at the bottom.
 44. A system according to claim 40, be providedwith a pump, automatically activated by, for example, a level sensor ormoisture sensor, and powered from a battery charged by e.g. solar orwind energy.